score:8
As a tall person with an ideal weight, you shouldn't worry about the width of the seat. What you should worry about is the pitch of the seat, which will give you a better idea of the leg room.
If you wonder what a seat pitch is:
Seat Pitch is the distance from any point on one seat to the exact same point on the seat in front or behind it. While it is not the exact equivalent of "legroom", it does give a very good approximation of how much seat room you should expect. Bottom line: the more seat pitch the better.
China airline's 777 in economy has a seat pitch of a 32", which is pretty standard in many regular airlines around the world (±1").
Is it comfortable? not really for a guy your height, but almost all other airlines have similar seat sizes and your best option is to get a seat in the emergency exit row where leg room is much better. Other option would be upgrading yourself to premium economy or business.
Upvote:5
A lot of airlines have 17" wide seats, some 17.5, but usually above that requires paying extra for 'premium' economy (different names with each airline).
Width as a comfort factor comes to play if your posterior is wide. While obesity is a primary factor, there are plenty of people who simply have wider hip bones. And long term pressure on your sides builds discomfort.
While I am not tall, I find seat pitch to be my primary comfort factor. More legroom is king and I would choose a narrow seat with more pitch, then a wider seat with less pitch.
Of course the actual seat used also is big factor, some are better padded and thus more comfy. But alas the need to lighten the load has seen the older well padded seats replaced with lightweight lightly padded versions.